Dynamically changing the size of nodes?

[John Baker <john AT jdiligence.com>]

It’s probably simple but can’t find it in the docs.

I want all my nodes & edges to grow or shrink programatically based on other 
values such as ‘range’ and ‘capacity’.

What are the attributes I need to manipulate? What are the units? My ranges 
are usually 0.0 to 1.0.

Thanks,
John